This invention relates to a fluid pressure indicator for providing visual indication whether or not the magnitude of a fluid pressure condition is above a predetermined minimum value.
More particularly, the inventive indicator is an improvement over a prior art indicator manufactured by Clippard Instrument Laboratory, Inc., 7390 Colerain Road, Cincinnati, Ohio 45239 and sold under the designation "Pneumatic Pressure Indicator IND-3," and hereinafter referred to as "the Clippard indicator." The Clippard indicator is partially disclosed in an undated bulletin designated "Technical Data Sheet 8001" and comprises a black matrix having seven holes therethrough, a bright pin member having seven pin elements located one in each of the seven matrix holes, a plunger having a first end exposed to fluid pressure and a second end confronting the pin member and a transparent bezel providing a viewing end and located in front of the matrix. The Clippard indicator also entails an internal spring which, when the fluid pressure is low, holds the pin member in a first position in which the pin elements are deeply set in the matrix holes and are thus optically masked, but which is resiliently flexed when the fluid pressure is sufficiently high, to permit the plunger to move the pin member to a second position in which the pin elements are displayed in the bezel. When the fluid pressure is reduced the spring returns the pin member to its first position.
The Clippard indicator further has a resilient sealing element seated in a groove around the plunger and in sliding sealing engagement with an internal surface of a metal body in which all of the other parts of the Clippard indicator are located.
The metal body of the Clippard indicator has an aperture which has an end exposed to the fluid pressure source and another end in open communication with the plunger.
The indicator of the present invention is an improvement over the Clippard indicator in that the spring of the Clippard indicator is eliminated as is the requirement for a sealing element in sliding fluid sealed engagement with the metal body. Both of these features of the Clippard indicator are conducive to shortened indicator life, due to possible spring failure or changed operating characteristics over many cycles of operation and due to possible seal failure.
Important objects of the present invention are to provide an indicator which is an improvement over the prior art in that the inventive indicator is both simplified and of more reliable constant operating characteristics over an indefinite number of operating cycles.
The present invention eliminates the spring and the sliding fluid sealed engagement which are required in the Clippard indicator.
The manner in which the present invention achieves the aforesaid objects, and others, will appear hereinafter.
The prior art also teaches a display in which a movable character is located behind a translucent window and hence is invisible when spaced away from the window, but becomes visible when adjacent the window. Greene U.S. Pat. No. 3,372,501 discloses this feature. The pertinence of the Greene patent will appear hereinafter.